Field
Embodiments related to optical elements having electro-optic variable apertures, are disclosed. More particularly, an embodiment related to an electro-optic variable aperture lens for use in a camera, is disclosed.
Background Information
Camera modules have been incorporated in a variety of consumer electronics devices, including smart phones, mobile audio players, personal digital assistants, and both portable and desktop computers. A typical camera module includes an optical system used to collect and transmit light from an imaged scene to an image sensor. The optical system generally includes at least one lens associated with one aperture. The lens collects and transmits light. The aperture limits the light collected and transmitted by the lens, and is therefore termed the stop aperture, or alternatively, the entrance pupil) aperture. The effective diameter of the stop aperture combined with the lens focal length determines the “F number” of the lens. A lens with a lower F number produces a brighter image than a lens with a larger F number and, as a result, reduces the image noise in a low light scene. However, as the F number is reduced, the lens depth of field decreases and, as a result, lens aberrations increase. Thus, there is an optimal stop aperture diameter, dependent on the lens and the scene being imaged, to minimize image noise and maximize image resolution.
In most portable consumer electronics devices, minimizing device profile is an important design goal. Accordingly, device profile requirements generally prohibit the use of an iris diaphragm as a variable stop aperture. Thus, product designs often aim to minimize the device profile, known as z-height, by fixing the aperture diameter in the optical system for a particular zoom factor. This design choice minimizes the F number without noticeably affecting achievable resolution, both from design and manufacturing standpoints. As a result of this design paradigm, users have been unable to adjust and optimize the F number for a particular scene in a mobile application.